Why are manhole covers round and not square in shape?

Manholes are round because “it is the best shape to resist the compression of Earth around it.” Round shapes are easier to manufacture than square or rectangular shapes, and because manhole covers are heavy, being round makes them easier to move from place to place (just roll them!).

Why are manhole covers round math?

But there’s actually a cool geometry reason behind the design: Circle-shaped things can’t fall through a hole shaped like themselves, but other shapes can. The easiest way to understand this is to start off with something that can fall through.

Why is the manhole circle and not triangle?

The most commonly cited reason is that the circular shape of the cover ensures that the cover doesn’t fall through the opening itself. This actually makes sense, since rectangular/square covers would fall through the opening if inserted diagonally into the hole (Source).